If you're a 1L and it's an open book exam, your highest RoI right now would probably be from learning about what the hell is expected of you on a law school exam in general (getting to maybe, guides here, etc.). Maybe a practice exam, but don't get so mired in practice problems you lose sight of how to do practice problems well.

Re-read your outline over and over and over and over, making hand notes in areas you realize you missed something, etc. Saturate, run some practice questions, eat a high quality meal the night before (steak, whatever), orgasm, and get some sleep.